Tuesday, December 18, 2012

Furry Rivers

I was just here three weeks ago and it didn’t look anything like this. Everything is covered in a fluffy algal fur. The angulated lines of the rocks that make up this rapid are softened and billow in the flow. The fast moving water mashes the algae to the boulders and form a mosaic of quarter sized green and brown patches that quiver in the current. If I didn’t know I was in Deer Creek, I could easily mistake my surroundings for another planet, it looks so alien.
This is a normal seasonal progression for our streams. We see an explosion of algal growth when the balance of nutrients, sunlight and grazing is thrown off center with autumn leaf fall, and colder temperatures. Deciduous trees drop their leaves each fall and many of them end up in streams. This increases the amount of sunlight reaching our streams and increases the amount of nutrients in our creeks, which create conditions excellent for an explosion of algal growth. At the same time, temperatures drop, and algae grazing insets reduce their activity, so the streams control mechanism of excess algal growth stalls. The system gets temporarily off balance, algae cover everything, and our rivers get furry.
We are familiar with the terrestrial passage of the seasons, and maybe take how life responds to changes in sunlight intensity, which affects temperatures, for granted. It is a more pronounced change in our streams because we don’t live there. Even though streams are familiar, their underwater views are foreign so changes appear less subtle, more dramatic and more easily noticed. What most people don’t recognize, and I often forget, is that streams have seasons too.
Time goes on, and seasons come and go, even in our rivers and streams. I feel fortunate to watch the underwater seasons pass, generally in step with and definitely linked to the terrestrial ones, which ultimately are affected by cosmic events. But the underwater seasons of our rivers and streams are unique in how they present, and I get to witness the otherworldly seasonal progression.